The Gauntlets of Flaming Fury, a magic item from the WoTC adventure Baldur's Gate: Descent into Avernus, have the following property amongst others:
While you wear both of these steel gauntlets, any non-magical weapon you grasp with either gauntlet is treated as a magic weapon.
Would those Gauntlets make Improvised Weapons be treated as magical?
Reminder on Improvised Weapons rules:
Sometimes characters don't have their weapons and have to attack with whatever is at hand. An improvised weapon includes any object you can wield in one or two hands, such as broken glass, a table leg, a frying pan, a wagon wheel, or a dead goblin.
Often, an improvised weapon is similar to an actual weapon and can be treated as such. For example, a table leg is akin to a club. At the DM's option, a character proficient with a weapon can use a similar object as if it were that weapon and use his or her proficiency bonus.
Best Answer
Only your DM can answer this.
Much like the linked questions in comments, the rules aren't clear enough to dictate a general case answer, even if we resort to plain-meaning-of-words interpretation. There is a solid case to be made in either direction, and only a specific DM can adjudicate it for their specific table.
Option 1: They don't make improvised weapons magical:
The defining feature of an improvised weapon is that it is not, in general, a weapon. Using an object as a weapon may have some weapon-like effects (such as dealing damage), but is rather like trying to use your car as a boat. It might "work", to some degree, but a typical car is not boat-like enough to be considered a boat, and you will not get the boat-level results a person making the attempt might expect.
Option 2: They do make improvised weapons magical:
Whatever an object might have been an instant before it was used as an improvised weapon, at that moment it is a specific type of weapon. Though more awkward and less effective than a proper weapon, it's still a weapon, and that is the only relevant restriction described for the gauntlets. Without the gauntlets the item might offer unimpressive damage, and with the gauntlets it simply offers unimpressive magical damage.