As it seems you already know what's gambling and gambling is haram in Islam. So, let's only focus on discussing if this case is gambling or not.
This has everything to be declared as gambling, although company is not playing in it, it will give away the prize anyway, its the people participating who are gambling. But, company is CONDUCTING this gambling which as muslim is not supposed to involve in, i.e: supporting or conducting any haram thing. Same as if someone holds a drinks party where some haram drink is served to the attendances, but the host don;t drink because it's haram. Still, he is providing and helping for this haram to happen. Similarly if a company uses such tactics for promotion, it's gambling and should be avoided.
O you who believe, intoxicants, Maisir, sacrificing for idols and
making decisions based on games of chance are filth from the work of
satan, so avoid these things and you may prosper. Satan desires to
create enmity and hatred amongst you through intoxicants and gambling
and to stop you from praying and remembering Allah. So will you
abstain from these things? Quran 5 90-91
They ask you, O Muhammad, concerning alcoholic drink and maysir(gambling).
Say: they contain great sin and benefit for people, but their sin is
greater than their benefit. And they ask you what should they give to
charity? Say: that which is more than their need, And so Allah shows
you wisdom so that maybe you will think Quran 2 219
Instead of this, you can use any other tactics like first 10 will get this next 10 will get this or something like this. Or anything else.