I'm not sure your "cooking with water" expression would be easily understood.

I think, it is important to know the entire German sentence.

I know the expression as "die (anderen) kochen auch nur mit Wasser", which means, they have no other resources than we do.

"we are no different from the rest" is certainly an equivalent to "wir kochen auch nur mit Wasser" on its own, but has a negative touch in a business context (we are not better than the others). If the sentence is "Im Gegensatz zu anderen haben wir eine Lösung zu ... und wir kochen auch nur mit Wasser.", than it is a positiv remark: We make more out of the given resources than others.