If they are not devout, their membership may or may not be in jeopardy. It very much depends on what the person is doing. Members who do a very poor job of living the standards of the church can be exhorted and disciplined. The most severe method of "discipline" the church can apply is excommunication. (That is, a revoking of membership.) To be excommunicated is considered a very serious thing and requires the commission of what we consider some very serious sins (for example, murder or many sexual sins) or open rebellion against the church. (Drinking coffee and smoking are considered serious, but do not, generally, merit excommunication.) Aside from the loss of membership there is also disfellowshipping. To be disfellowshipped means to have the privilege of ministering in the church revoked. Our church has a "lay ministry". That is, all functions within the church are performed by unpaid members. The teaching, the preaching, etc. Every member generally has a responsibility (all are supposed to). However, disfellowshipped members do not and can not have such responsibilities. (There is certainly a little more to this, but I think this is a fairly accurate description.) Drinking coffee and smoking, I don't believe, generally lead to disfellowshipping. (I believe.) Less discussed as a form of discipline is the revoking of the temple recommend. That is, one loses the privilege of going to worship in the temple. This too, is considered very serious, but less so than disfellowshipping. Drinking coffee and smoking most certainly will prevent one from receiving a temple recommend and if one has previously obtained one, will lead to its being revoked. Drinking and smoking will also prevent one from being initially baptized. Once a member though, it does not lead to one's being thrown out in and of itself. Generally, it is hoped in all cases that those disciplined will take the discipline as impetus to correct their behavior and come back into full fellowship.

Once you are a member of the Church, every case like this is treated on its merits; and it would be hard to answer the Q satisfactorily for this reason. I, personally, do not know of anyone being excommunicated nor disfellowshipped for not living the Word of Wisdom code - which is what you are addressing. On the other hand, these things will prevent someone's being baptized; Yes. They will also prevent a member from being worthy to enter the temple, and such would not receive a temple recommend necessary to enter. Once one is a member it is hard to generalize on worthiness. There are just so many factors comprising the worshipper of God. I once had a stake president confide in me that his stake had a case [for a much more grievious matter than that you mention here] brought before the high council, where all the evidence pointed towards excommunication. Yet after much hearing, he and his counsellors took the matter privately to the Lord in prayer, and were prompted that they should take no action against the particular member. So, only God knoweth as He doeth. Only He knows the heart.