Papier maché with toilet paper
Toilet/tissue paper is processed in such a way as to be as absorbent as possible.  So, by soaking it in water the paper fibres expand and when they dry, they shrink back and stick well to each other. Other papers, like inkjet papers, are coated, or otherwise processed, in such a way as to reduce the absorption of ink. In your case this means that if you try to make papier-mâché with such paper and just water the fibres won’t be able to absorb enough water in order to expand and stick well together when dry.

So you can use toilet/tissue paper and just water to make papier-mâché but for less absorbent paper you may need some adhesive (e.g. starch from flour).