For me, the biggest problem while being on dialysis was the fluid restriction. Typically, people on dialysis need to restrict their fluid intake to a liter. This includes water, tea, coffee, curd, dal, rasam, ice cream etc. Anything that is fluid at room temperature is counted as fluid. All told, the fluid intake should typically not cross a liter. For people who pass urine, this could be higher.
I find that having a plan on the fluid helps a lot. Rather than drinking at any time, having a plan on when to drink what and how much helps manage this much better. One thing which is commonly recommended is to measure out your allowed quantity of water in a bottle and drink only from that. When you drink something other than water, discard an equal amount from the bottle. Plan your day so that the bottle lasts you till you go to sleep.
Another good way is to write out your fluid plan for each day. Think about what's important for you. Let's say, it is important for you to have 3 small cups of tea - one early in the morning, one at around 11:30 and another cup in the evening, write these three things down. This could probably come to about 300 ml. Put in about 100 ml of water after every meal. The total comes to 600 ml. You still have 400 ml to play with for different things. The key is to fix up the time, the quantity and what exactly you would like to have and write this down and follow it as much as possible.
By doing this, you have no surprises. In case you feel like having a gulp of cola at dinner, you can skip one round of tea. I believe very few things are entirely out of bounds for people who get thrice weekly dialysis. You can have everything in limited quantities provided you plan it well.
If there is something you really relish which is high in potassium, ask your doctor if you can have a small quantity during the first half an hour of dialysis. If you are otherwise compliant and dialyze regularly without skipping the prescribed sessions, you can afford to take some liberties during the first half an hour of dialysis since the dialysis will remove the excess potassium during the treatment. Of course, every individual is different. So, please check with your nephrologist or dietician before doing anything out of the ordinary!