You want to rope off one item and then say what holds for everything outside it.
序 · The move
1Put the item you are fencing off between 除了 and 之外.Is the thing inside the bracket the one set aside, not the thing the predicate is about?
2Write the second clause about the remainder.Does the clause speak of what lies OUTSIDE the fence, never the fenced item itself?
3Pick the predicate that sets the direction: 不/沒 for nothing else, 還/也 to add more, 都 to sweep all the rest.Negative remainder (pure exception) needs 不/沒; additive needs 還/也; whole-remainder sweep needs 都.
Apart from drinking water, my older sister normally drinks no other beverages.
界 · Boundary
除了…還/也…
除了…之外…不/沒… ropes off the one item and leaves nothing beyond it (only that one). 除了…還/也… ropes off the one item and stacks more on top (that one, and more besides). The second-clause word sets the direction.
除了…（以外）…都…
之外 and 以外 do the same job (之外 reads more written); the difference is the predicate. 都 sweeps the whole remainder under one statement; 不/沒 denies the remainder; 還/也 adds to it.
姐姐平常喝水之外，不喝其他的飲料。 → 姐姐平常除了喝水之外，不喝其他的飲料。 (The fence opens with 除了; 之外 alone leaves the bracket unbuilt.)
姐姐平常除了喝水之外，還喝其他的飲料。 → 姐姐平常除了喝水之外，不喝其他的飲料。 (還 stacks more on top, so it says she drinks others too; the exception sense needs 不 to deny the rest.)
姐姐平常喝水除了之外，不喝其他的飲料。 → 姐姐平常除了喝水之外，不喝其他的飲料。 (除了 leads the fenced item; it does not trail it.)
English says apart from X with one phrase and free placement; Chinese splits the bracket across two fixed slots (除了 … 之外) and then leans the whole sentence on the second-clause word (不/沒, 還/也, 都) to fix the direction.