For すし actually it does not quite matter. Both are fine. But for お酒, we usually add お. One of the reasons is that leaving out the お can create confusion between alcohol and salmon (refer to the discussion in this thread).
お酒（さけ） means general alcoholic drinks. The English term "sake" generally refers to 日本酒（にほんしゅ） which is one type of お酒. アルコール means alcohol, where it can be used in drinks or medical uses. アルコール飲料（いんりょう） means alcoholic drinks.