Look at the "Target" line of the spell. Unless attended objects are listed as valid targets, you can't target them. For example, Magic Missile cannot target objects, only creatures.
On spells that target creatures, if there is a save and the creature rolls a 1, that creature's objects may be affected. See "Damaging Magic Items" on page 459 of the core rulebook.
If the spell creates a weapon-like effect (such as Flame Blade), that effect might be able to target such things via the Sunder mechanic.
Barring special abilities or feats, Sunder is melee only, so you might be able to do it with a melee touch attack, but not with a ranged touch attack or ray such as disintegrate, unless you're using some sort of optional called shot rules. See threads on Ranged Sunder, like this one or this one or this one with extra JJ.
Some spells, such as Grease specifically allow attended objects to be targeted, but unlike unattended objects, attended objects get a saving throw