If there is sex in this poem, it isn’t obvious. In fact, sex doesn’t seem to enter the picture at all in “God’s Grandeur.”
But wait, maybe it does.
In the biography Gerard Manley Hopkins: A Very Private Life, author Robert Bernard Martin argues that Hopkins often uses sexual metaphors to talk about his religious feelings. In Julia F. Saville's book, A Queer Chivalry: The Homoerotic Asceticism of Gerard Manley Hopkins, Saville argues (as you might have guessed from the title) that Hopkins’s poetry contains homoerotic aspects.
How does that relate to this poem? Well, one could imagine that phrases like "man’s smudge" and "man’s smell" might have something to do with sex. What do you think?